The present invention generally relates to steering angle sensors and more particularly relates to systems for attaching a steering angle sensor in a vehicle.
An attachment of this type is e.g. known from U.S. Pat. No. 5,002,404 A which, especially in FIG. 2, discloses an attachment of a steering angle sensor in a vehicle including a steering column and a steering spindle pivoted therein, wherein a sensor housing is held unrotatably in the area of the steering spindle bearing.
The basic design of steering angle sensors is known in the art, see DE-OS 196 01 964.8, for example. In systems for controlling vehicle dynamics, especially, for controlling the yaw rate (in ESP programs), it is necessary to sense the steering angle with high precision and without faults. Normally, steering columns and steering angle sensor connections cannot be easily manufactured with the degree of precision desired. This is due to: high costs, radial adjustment of the steering wheels, axial adjustment of the steering wheels, clamping function of the adjustment, mounting tolerances in the vehicle, steering forces cause elastic deformations.
According to the current state of the art, the bearings between the steering shaft and the vehicle fixing points must be mounted in rubber, at least in part, to provide ease of motion of the steering unit and isolate it from vibrations.
An object of the present invention is to provide an attachment of a steering angle sensor wherein an exact allocation of the axes of rotation of shaft and sensor is maintained under all operating conditions, in spite of the above requirements.
The principle of the present invention basically includes that the center line of the sensor housing (1) and the axis of rotation of the steering spindle (2) in the sensor area are congruent. This way the influences which cause an offset positioning of the steering spindle bearing (6) and, thus, of the axis of rotation (15) of the steering spindle (2) in relation to the sensor housing will not take effect because the position of the sensor housing (1) is displaced accordingly along with the offset positioning of the axis of rotation (15). The same applies to the entraining member (4) which is also displaced along with the offsetting of the axis of rotation (15) and, thus, maintains its correct allocation in relation to the sensor housing (1). In contrast hereto, the sensor housing is rigidly connected to the vehicle chassis in previous disclosures so that a movement of the longitudinal axis of the spindle in relation to the center line of the sensor housing could lead to wrong measurements or even damages to the sensor.
A particularly tight coupling of the steering angle housing to the position of the steering spindle is achieved by the present invention. This is because the outside bush of the roller bearing normally has only very narrow tolerances in relation to the inside bush and, hence, the position of the steering spindle or shaft (2). Because the outside bearing bush and, thus, also the sensor housing precisely follows the radial movement of the spindle axis, any possible tumbling movements of the spindle have no influence on the position of the sensor (1) in relation to the spindle (2).
As far as the attachment of the sensor to the outside bearing bush is concerned, said may be achieved by means of a connecting member which is rigidly seated on the outside bearing bush or is detachably connected to the latter. The connecting member can also be integrally connected to the outside bearing bush so that the outside bearing bush simultaneously represents the connecting member to the sensor housing.
Special advantages of the present invention are realized when the swing support (8) is rotated about the fulcrum (16), and simultaneously, the tiltable part of the steering spindle is also tilted. This maintains the position of the sensor housing (1) in relation to the spindle or shaft (2) such that it does not change. It is not absolutely necessary that an elastic torsional bar, e.g. made of rubber, is provided in the swing support (8). The present invention is very favorable even if the sensor housing is attached directly to the swing support and the said has no elastic torsional bar, because due to the spatial arrangement of the sensor directly at the bearing, the sensor will always follow the radial movements of the steering spindle which may be caused by conditions of unbalance, impacts on the vehicle chassis, or radial forces applied to the steering wheel, for example. This way, a possible tilting of the bearing will not effect any change in the distance between the outside bearing bush and the axis of rotation of the spindle (2).
It is especially favorable for the present invention that the attachment according to the present invention in addition may be used as an adapter for adapting the sensor housing (1) to the steering spindle. It is advisable in this respect to detachably couple the steering sensor housing with the adapter so that, in case of need, it is easily possible to replace the housing or adapt it to changed conditions.
A preferred embodiment is recommended for the design of the adapter which is generally composed of a cylinder-shaped sleeve that is fitted to the outside bush of the roller bearing (6), e.g. press-fitted, or connected detachably or undetachably in any other fashion. Succeeding the cylinder-shaped wall in a radial direction is a generally annular-disc shaped projection to which the sensor housing may be attached. The roller bearing or antifriction bearing should preferably have a design resistant to tilting so that tilting of the outside bearing bush with respect to the inside bearing bush and, hence, the spindle is prevented in any case. This may be performed by using several parallel balls (see FIG. 1) or long cylinder-shaped roll bodies, or other arrangements known in the art.
Regarding the connection between the outside bearing bush and the sensor housing, the adapter acts as a connecting member which has already been explained hereinabove, and the adapter can be integrally connected to the outside bearing bush, or the outside bearing bush is passed out of the bearing as an adapter. As explained hereinabove, the adapter may also be integral with the outside bearing bush. Provision should be made in attaching the sensor housing to the adapter that the sensor housing can be aligned centrically or adjusted in relation to the axis of the steering spindle before the attachment action. This may be done by a detachable connection, for example, which in the transverse plane relative to the longitudinal axis of the spindle, permits a certain freedom of motion of the housing relative to the spindle axis prior to the fixing operation, e.g. by a sufficiently large configuration of the attachment holes.
The above-described features are generally based on the fact that the connecting element or angular element is rigidly connected relative to the outside bush of the bearing and the sensor housing is rigidly connected relative to the angular element.
In a preferred embodiment, the sensor housing is floatingly but unrotatably supported, preferably in relation to the swing support (8), in the transverse plane relative to the spindle axis. This may e.g. be effected by radially pointing grooves at the projection of the angular element that extends in a radial direction, into which corresponding projections of the sensor housing project. However, care must be taken in this case that the sensor housing is supported in a radial direction relative to the spindle surface or the spindle axis so that the housing is able to follow the unbalance movements of the spindle.
The support may be achieved by a suitable bearing, for example, whose outside bearing ring makes catch at the sensor housing. Further, care must be taken that the housing is secured in position in relation to the spindle bearing in a longitudinal direction of the spindle axis. This securing-in-position may e.g. be effected by a spring (10) which applies a resilient force to the sensor housing in the direction of the spindle bearing. However, other holding elements such as metal sheets which permit a certain degree of movability of the sensor housing vis-à-vis the bearing housing may also be used. It is not necessary though that the angular element acting as an adapter is rigidly connected to the outside ring of the spindle bearing. It is also possible that the sensor housing is sufficiently displaceable in the radial plane in relation to the facing radial surface of the bearing housing, that means at least in the X-axis, possibly also in the Y-axis. However, there must not be any changes in the unrotatable connection between the sensor housing and the bearing housing. A construction of this type is especially suitable when the outside housing part of the bearing housing is sprung by rubber inserts vis-à-vis the actual roller bearing so that the spindle moves relative to the outside housing part. However, this is no necessity with regard to the suitability of the construction mentioned before.
As explained already, the guide grooves for the sensor housing may be provided in the radial outside surface of the housing itself and in the radial projection of the angular element (adapter 3). It is, however, also possible to install a special adapter disc which is connected to the sensor housing, on the one hand, and is slidable relative to the radial surface of the spindle bearing, on the other hand.
In a preferred embodiment, the housing, too, is displaceable in relation to the adapter disc in a radial direction, with the two directions of displacement between the spindle bearing and the sensor housing being respectively vertical to each other in the radial plane with respect to the adapter disc. The result is that the sensor housing is displaceable in two directions (X-direction and Y-direction) with respect to the bearing in the radial plane and, nevertheless, is arranged unrotatably with respect to the spindle bearing.
a possible design of the entraining member (4) is e.g. disclosed in application P 198 22 825. This measure, too, contributes to eliminating the effect of an impact in the steering spindle (2) or a radial offset of the housing.